Concrete is currently utilized to make a number of building products including, but not limited to, manufactured stone veneer, cementitious siding and cementitious roofing tiles. U.S. Pat. No. 6,790,544 to Schmitz, U.S. Pat. No. 5,797,238 to Berntsson et al, U.S. Pat. No. 5,435,949 to Hwang, U.S. Pat. No. 4,877,656 to Baskin and U.S. Pat. No. 4,235,948 to Holmes and published U.S. Patent application 2004/0175514 to Stiattesi are all exemplary of state of the art concrete products and their methods of production.
In the past a manufactured stone veneer has been formed utilizing a mold having cavities with shapes simulating real stone. More specifically, the state of the art manufacturing process generally comprises painting the mold cavity with a pigmented slurry consisting of water, cement, certain iron oxides for color and a polymeric binder. Next, concrete is vibrated into the cavity over the pigmented slurry. The material is then allowed to cure and set before being removed from the mold. Upon removal, the product comprises a body consisting of an ornamental facing layer formed from the pigmented slurry and a concrete substrate layer formed from the concrete.
As the concrete is vibrated within the mold M, aggregate and cement paste migrate downward and air bubbles B are typically driven upward (see FIG. 1). It should be appreciated, however, that the concrete layer C includes a high viscosity, compacted aggregate that resists the upward movement of the air bubbles B. As a result, at times one or more air bubbles become trapped at the interface I between the pigmented slurry S and the concrete C. This results in a number of detrimental effects.
More specifically, the pigmented slurry and resulting ornamental surface layer are typically thin. Air bubbles underneath the surface along the interface between the two layers significantly weaken the ornamental surface layer. As a consequence, the surface layer may become damaged during removal of the product from the mold, during packing of the product for shipping, during shipping, during installation or even during handling at any time. Where the damage is severe, the product must be scrapped. Further, while less severe damage may not require scrapping of the product, it can adversely effect the service life and customer satisfaction with the product. More specifically, small air bubbles can lead to the formation of small holes in the ornamental surface layer. Such holes deleteriously affect the natural ornamental appearance of the product.
The present invention relates to a concrete product and a method for its production that substantially reduces or eliminates problems produced by air bubbles becoming trapped along the interface between the pigmented slurry and the concrete during production of concrete products. As a result, the concrete products of the current invention are produced without surface holes and have a more natural appearance.